The MRI apparatus is an apparatus that measures an NMR signal generated by the object, especially, the spins of nuclei which form human tissue, and images the shapes or functions of the head, abdomen, limbs, and the like in a two-dimensional manner or in a three-dimensional manner. In the imaging, different phase encoding and different frequency encoding are given to NMR signals according to the gradient magnetic field, and the NMR signals are measured as time series data. The measured NMR signals are reconstructed as an image by a two-dimensional or three-dimensional Fourier transform.
If an object moves during the measurement of NMR signals, body movement artifacts are caused in the reconstructed image. A non-Cartesian sampling method is known as an effective method to suppress the occurrence of body movement artifacts. Examples of a non-Cartesian sampling method include a radial method (for example, refer to NPL 1), which acquires echo signals required for the reconstruction of one image by performing sampling radially while changing the rotation angle with approximately one point (generally, the origin) of measurement space as the rotation center, and a hybrid radial method (for example, refer to NPL 2 and NPL 3), which is a combination of the radial method and phase encoding and which divides the measurement space into a plurality of different blades in a sampling direction, samples the blades, and performs phase encoding within the blades.
In particular, the hybrid radial method is a method of filling k space while rotating a plurality of k-trajectories (trajectories of k space; blades), which are obtained in one repetition time (TR) by the fast spin echo (FSE) method, every TR. In the hybrid radial method, each blade certainly fills the center of k space. There is a technique of detecting the rotation or translation of the object using the overlap portion and correcting the body movement (for example, refer to NPL 3).
In the technique disclosed in NPL 3, however, the spatial resolution of an image for correction, which is generated from the overlap portion of k space used to detect body movement, is generally lower than that of a diagnostic image used for diagnostic purposes. For this reason, characteristic points, such as a structure, may not be detected in the image for correction. In particular, at the slice position where the cross section is almost circular, such as the head, the body movement of an object may be incorrectly detected even if the object does not actually move and accordingly an incorrect image for correction may be generated.
In multi-slice imaging, there is a technique for removing a slice from which an incorrect image for correction has been generated (hereinafter, referred to as an incorrect slice) and recalculating a correction parameter of the removed incorrect slice from correction parameters of other slices (for example, refer to PTL 1).